1. Field of the Invention
The present invention relates to a lens barrel and image-pickup apparatus having a focus mechanism and a barrier mechanism that includes a barrier member disposed on the front side of the lens barrel for protection of an image-taking lens.
2. Description of the Related Art
As a lens barrel mounted in a camera, there is conventionally known a lens barrel having a barrier mechanism and a focus mechanism. The barrier mechanism is for causing a barrier member disposed on the front side of the lens barrel to open and close with advancing and receding movements of the lens barrel in the optical axis direction between an image-taking position and collapsed position thereof. When the lens barrel is in the collapsed position, the barrier mechanism closes the barrier member to protect a lens group that is disposed on the front-most side of the lens barrel. The focus mechanism is for driving the front-most side lens group in the optical axis direction for focus operation.
In the following, an explanation will be given of a lens barrel having a barrier mechanism and a focus mechanism according to Japanese Laid-Open Patent Publication (Kokai) No. H06-027519. It should be noted that reference numerals used herein are those shown in the Patent Publication No. H06-027519.
First, the barrier mechanism will be explained. The barrier mechanism is constructed of a drive ring 4 disposed between barriers 2, 3 and a barrel frame 1; springs 5, 6 hooked between the barriers 2, 3 and the drive ring 4; and a spring 7 hooked between the drive ring 4 and a dowel 1c of the barrel frame 1. The barriers 2, 3 are opened and closed with rotation of the drive ring 4.
Next, an explanation will be given of the focus mechanism. In the focus mechanism, a bar 9 serving as a guide is supported by a frame (not shown) for linear movement and is adhered to a barrel unit 8, and a pin 10 disposed in contact with a cam 11 is fixed to the barrel unit 8. With rotation of the cam 11, the barrel unit 8 is caused to move in unison with the bar 9 in the optical axis direction for focus operation. The lens barrel is designed that the bar 9 is in contact with a protrusion 4c of the drive ring 4 when the barrier is not fully opened, thereby preventing further advancing movement of the barrel unit 8 until the barrier is fully opened.
With the lens barrel proposed in Japanese Laid-Open Patent Publication (Kokai) No. H06-027519, however, the guide for guiding the movement of the barrel unit 8 in the optical axis direction and a movement stroke (focus stroke) of the lens group must be provided behind the drive ring 4. In other words, a focus stroke area and a barrier opening/closing operation plane must be arranged in series as viewed in the optical axis direction (on the lens group side of the drive ring 4), which poses a problem that the lens barrel is large in length (collapsed length) in the collapsed position. Furthermore, since the bar 9 serving as the guide for guiding the movement of the barrel unit 8 in the optical axis direction is adhered to the barrel unit 8, the lens barrel is disadvantageous in construction from the viewpoint of securing the required parallelism between the lens optical axis and the bar 9.